Testing - Concrete Mix Design, Quality Control and Specification - page 185

test on concrete is conducted on saturated specimens. The ASTM C1202 test
provides an electrical indication of the test concrete's ability to resist chlo-
ride ion penetration on vacuum-saturated 50 mm thick specimens. ASTM
C1202 involves subjecting the concrete specimen to a 60 volt potential for
6 hours and measures the ease of which concrete allows charge to pass
through it. This is affected by the density of the pore structure, the presence
of insulating or conducting components and the availability of negative ions
within the pore solution (Cao et al., 1996). Although concerns exist over
the relevance of the test, there are abundant comparisons that show good
correlation with chloride diffusion and other transport properties.
The test is often called the “rapid chloride permeability test”, but it does
not measure chloride movement or permeability. It is a saturated resistivity
test. An often forgotten point in the test procedure debate is the impor-
tant role that resistivity plays in the propagation phase of corrosion. In our
opinion, if one is intending to use this test, a little bit more effort would
enable both resistivity and migration to be measured using virtually the
same equipment following the NT Build 492 test procedure.
As the ASTM C1202 or Coulomb test is a saturated resistivity test, the
result can be obtained virtually instantly and does not require 6 hours.
Simple bulk resistivity tests on compliance cubes or cylinders can be used
to provide valuable resistivity data with very little effort or expense.
7.6.9 Corrosivity
Almost every test for durability assessment discussed in this section has
been a penetrability test measuring one or more transport property of
concrete. However, there are some methods of enhancing durability by elec-
trochemical methods that do not necessarily change transport properties,
such as corrosion inhibitors. ASTM G109 tests the effect of admixtures on
macrocell corrosion in concrete subjected to wetting and drying with a 3%
sodium chloride solution. As the chloride solution penetrates the 25 mm
concrete cover by absorption and diffusion, the test measures both pen-
etrability as well as any effect of increasing the chloride threshold level.
The main problem is the time to complete the test that is equivalent to 150
coulombs of macrocell current in the control which can take over two years
in a decent quality concrete. Lollipop tests with centrally placed reinforce-
ment in a cylinder and monitoring corrosion with linear polarisation also
measure both penetrability and corrosion inhibition. Increasing chloride
concentration or reducing concrete quality may reduce the time required but
may give misleading results. Another difficulty in confirming the benefit of
corrosion inhibitors is the wide range of measured chloride threshold levels
as discussed by Ann and Song (2007). Trejo and Pillai (2004) proposed an
accelerated test for determining chloride threshold levels, which may be
useful in quantifying the benefit of accelerators.